Look, we have nothing against May-December pairings (hellllooo, Harrison and Calista), but there’s something Ben Gay-scented on the set of Gossip Girl. Well, two things, actually. Namely, Serena (Blake Lively) and Steven Spence (Barry Watson), and Rufus (Matthew Settle) and Ivy (Kaylee DeFer). Public service announcement time: we think it’s all a little arthritic, story-wise. In both cases, the pairs were slapped together with no explanation. While Rufus was Ivy’s faux..